When we describe events that happen in works of literature, what tense should we use?
Use the present tense -- the "literary present" -- to refer to fictional events.
Generally, we use the "literary present" to refer to fictional events.
The idea is that the work of art exists in a timeless way.
Hamlet, for example, always vacillates, so he IS always hesitant.
An exception might be the use of a kind of past perfect, where one fictional event is referred to in the past tense because it occurred before the present action.
For example, you might write:
"Tom induces his friends to paint the fence, a chore his aunt had assigned him that morning."
In this case, you use the literary present to describe the fictional event of "inducing."
But his being assigned the chore had happened earlier, so you use the past or past perfect.
Even though you use the "literary present" to refer to fictional things, you still use the past to refer to historical events.
"The novel explores the situation of soldiers in WW I, which devastated much of Europe."
Here is a good short .edu PDF that gives more details about the tenses used in writing about works of art: